1. Field of the Invention
This invention relates to a refractory fiber spatial structure and a method of manufacturing a refractory fiber-like material.
More particularly, this invention relates to a refractory fiber-like material, refractory fiber spatial structures constituted with the refractory fiber-like material, having a rigid form and capable of use for applications such as a heat-resistant filter, a chemical-resistant filter, an exhaust gas filter for a gasoline engine, a particulate filter for a diesel engine, a filter for a melting metal, a catalyst carrier, a carrier for fixing a microbe or an enzyme, a structure of a fiber-reinforced metal or the like, and a refractory fiber spatial structure with a heating element, and in addition, a method of manufacture thereof.
2. Description of the Related Art
Since a refractory fiber-like material has an excellent resistance to high temperatures, excellent resistance to corrosion, and a high tenacity, it is well known that the refractory fiber-like material is suitable for use as a heat-resistant filter, chemical-resistant filter, exhaust gas filter, filter for a melting metal, catalyst carrier, and structure of a fiber-reinforced metal or the like. For example, utilization of the refractory fiber spatial structure constituted of a refractory fiber-like material, as a high temperature dust collecting filter, is disclosed in "New Fibers and Fabrics in Hot Gas Fabric Filtration", Journal of Industrial Fabrics, Volume I, Page 44 to 48.
Since the conventional refractory fiber-like material and the conventional refractory fiber spatial structure constituted by the refractory fiber-like material are relatively flexible, they are suitable for applications such as a bag filter, but are not suitable for applications such as a fixed type filter, a fixed bed type catalyst carrier, a fixed bed type carrier for fixing a microbe or an enzyme or the like. Further, when the conventional fiber spatial structure is used as a structure of the fiber-reinforced metal, there is a disadvantage in that the structure is easily deformed when pouring a melted metal into the fiber spatial structure.
If a rigid form or structure is applied to the refractory fiber spatial structure, the refractory fiber spatial structure is not easily deformed, and further, the refractory fiber spatial structure constituted by the refractory fiber-like material has a large surface area within itself; namely, this structure is porous. Therefore, if a refractory fiber spatial structure having a rigid form can be obtained, this refractory fiber spatial structure would be a most suitable structure for the above-mentioned application. However, such a refractory fiber spatial structure having a rigid structure is not known as of now.
For example, U.S. Pat. No. 3,849,181 disclosed a refractory fiber-like material and a method of manufacture thereof. The refractory fiber-like material disclosed in this U.S. Patent is made by coating a fiber of refractory crystalline oxide with a glass, and this fiber includes a tow, a staple fiber, and a filament. This fiber-like material has a high tenacity because, when the fiber-like material is stretched, cracks on a surface of the fiber-like material rarely occur, compared with a fiber-like material manufactured only of the refractory crystalline oxide. However, since the form of this refractory fiber-like material is not rigid, a structure manufactured by this material can be easily deformed by an outer force. Further since this fiber-like material has little flexibility, it is difficult to form a fiber spatial construction into an optional form, which can be easily obtained when an conventional organic fiber is used. Even if the fiber-like material is protected by applying an oil or a resin onto the fiber-like material, only a woven fabric having a relatively simple design can be obtained. Further, the fiber-like material is easily broken by bending of the fiber-like material by guides and/or reeds during manufacture of the woven fabric, so that the quality of the obtained woven fabric, and the productivity thereof, become inferior. When a knitted fabric and a nonwoven fabric are formed by using this fiber-like material, the same problems arise, and it is impossible to effectively utilize the high tenacity of the fiber-like material except when the fiber-like material is formed in a state such that the fiber-like material is bent with a relatively small curvature to the knitted fabric or the nonwoven fabric. Further, the fiber spatial structure having a relatively simple design and used with this fiber-like material having little flexibility does not have a rigid form, and is flexible and easily deformed, so that this fiber spatial structure is not suitable for the above-mentioned application.
U.S. Pat. No. 3,385,915 discloses a method for manufacturing a refractory oxide fiber and a structure constituted by the refractory oxide fiber by impregnating a metal compound into an organic fiber or a structure constituted by the organic fibers, and burning them. U.S. Pat. No. 3,406,025 discloses a method for manufacturing a structure constituted by nitride fibers by impregnating a metal compound into a structure constituted with the organic fibers, and after resolving the organic fibers from the structure, burning the structure in a compound including a nitrogen. Further, U.S. Pat. No. 3,403,008 discloses a method for manufacturing a structure constituted by carbide fibers by impregnating the metal compound into a structure constituted by the organic fibers and burning the structure in a non-oxidative atmosphere. Since organic fibers having flexibility are used to manufacture basic fiber spatial structures in the three above-mentioned methods, refractory fiber spatial structures having an optional form can be obtained. However, the compression strength of the refractory fiber spatial structures manufactured by the three above-mentioned methods is extremely low, and the fiber-like materials constituting the refractory fiber spatial structure are relatively soft, and thus the refractory fiber spatial structures per se are also flexible. If the compression strength of the refractory fiber spatial structure is low, a shape or a form of the fiber spatial structure is easily destroyed, and therefore, the refractory fiber spatial structure having a low compression strength is at a great disadvantage in the above-mentioned applications, and the flexibility of the refractory fiber spatial structure is also not suitable for the above-mentioned application. The reason why the compression strength of the refractory fiber spatial structure manufactured by the three above-mentioned methods is low is not clear, but it appears that an inorganic material remaining after the organic material is dissolved forms a fiber in a cast-off skin state, and a binding force cannot be generated between inorganic fine particulates formed during the above-mentioned procedure.